The key to using cv.glm is that you have to have a fitted model object with

all the data to validate. In your case, that would appear to be a model

like this:

lm(base[,ncol(base)]~NDI)

where NDI is calculated from two bands in the dataframe base. However, if

the ground truth data is independently collected from the imagery (the

usual case), then there is no need to do cross validation - the model above

is all you need? If you repeat the model above for all pairwise

combinations of bands, then comparing the models using R^2 or some other

metric would tell you which band combination is superior.

Cheers

On Tue, Apr 10, 2012 at 6:01 AM, Motte wrote:Hey all,

I need some help with a cross validation. I'm new with R and as well with

statistics. I had a group work to create a tool for remote sensing class

that extracts the best bands of hyperspectral satellite images that

describe

vegetation. Its a regression between a linear function of using a

normalized

differenced index (i-j)/(i+j) while i and j are the bands (in the data

these

are the columns, expect the last column) and the ground truth data which is

listed in the last column in %.

We did a manual cross validation (described below), but as the code is too

long and confusing, we'd like to use the cv.glm function out of the boot

package. We've tried it several times, but we don't know how to do ist.

Could anybody help us?

This is our current code for the tool with a manual cross validation:

Thanks a lot,

Motte

--

View this message in context:

http://r.789695.n4.nabble.com/Package-boot-funtion-cv-glm-tp4545275p4545275.htmlSent from the R help mailing list archive at Nabble.com.

______________________________________________

r-help@r-project.org mailing list

https://stat.ethz.ch/mailman/listinfo/r-helpPLEASE do read the posting guide

http://www.R-project.org/posting-guide.htmland provide commented, minimal, self-contained, reproducible code.

--

Drew Tyre

School of Natural Resources

University of Nebraska-Lincoln

416 Hardin Hall, East Campus

3310 Holdrege Street

Lincoln, NE 68583-0974

phone: +1 402 472 4054

fax: +1 402 472 2946

email:

atyre2@unl.eduhttp://snr.unl.edu/tyrehttp://aminpractice.blogspot.comhttp://www.flickr.com/photos/atiretoo